PLT entry not initialized when loading a library, but called nevertheless

Sergey Prokhorenko
Wed Dec 12 08:07:00 GMT 2012

On 12.12.2012 02:09, Mike Frysinger wrote:
> On Tuesday 11 December 2012 13:23:22 Sergey Prokhorenko wrote:
>> So my question is (if you allow as I'm not really big expert in this
>> are) - can it be that this is dlopen/ld bug and am I in the correct
>> mail list after all? I think now that it is not ld bug, it seems that
>> ld stops loading but dl continues despite the error.
> you might be seeing lazy relocation.  do you get different behavior if you
> export LD_BIND_NOW=1 ?
> -mike
It makes no difference. I tried with it and LD_DEBUG=all and here's what 
I see in log after the omp_ symbol is not found for libC:

19225:     symbol=omp_set_num_threads; lookup in 
file=/usr/lib/i386-linux-gnu/ [0]
      19225:     /media/EXT/Work/ error: symbol lookup error: 
undefined symbol: omp_set_num_threads (fatal)
      19225:     file=/media/EXT/ [0];  destroying link map
      19225:     file=/media/EXT/ [0];  dynamically loaded by 
/media/EXT/ [0]
      19225:     file=/media/EXT/ [0];  generating link map
      19225:       dynamic: 0xf2fdb764 base: 0xf2f81000   size: 0x00064a28
      19225:         entry: 0xf2f8ffd0 phdr: 0xf2f81034  phnum:          7
      19225:     checking for version `GCC_3.0' in file 
/lib/i386-linux-gnu/ [0] required by file 
/media/EXT/ [0]
... few more checking
19225:     object=/media/EXT/ [0]
      19225:      scope 0: bin/mainapp 
/lib/i386-linux-gnu/ /media/EXT/ ...
19225: scope 1:...
19225: relocation processing: /media/EXT/
19225: symbol=_ZTVN10__cxxabiv117__class_type_infoE; lookup in 
file=bin/mainapp [0]
19225: symbol=_ZTVN10__cxxabiv117__class_type_infoE; lookup in 
file=/lib/i386-linux-gnu/ [0]
19225: symbol=_ZTVN10__cxxabiv117__class_type_infoE; lookup in 
file=/media/EXT/ [0]
19225: binding file /media/EXT/ [0] to /media/EXT/ [0]: 
normal symbol `_ZTVN10__cxxabiv117__class_type_infoE'

... here it continues to bind libA symbols, and after finishing that

19225: calling init: /media/EXT/

it calls init for the non-initialized module.

(Just to mention is the base module that calls dlopen and also 
contains basic methods used by all other libs.)

After destroying link map for libA the log shows that it is generated 
again, I just don't understand if loader continues to load libA or 
starts from scratch this time without bothering about libB/libC. Well, 
it ignores libB/libC in any case until init is calledfor libC.

Thanks, Sergey.

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